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Bezier S-Bend Factory

bend_s_bezier_factory(kcl) returns a cached cell function for cubic-bezier S-bends. Arguments width, height, and length are in µm. height is the lateral offset (negative flips the bend); length is the longitudinal extent.

import kfactory as kf
from kfactory.factories.bezier import bend_s_bezier_factory


class LAYER(kf.LayerInfos):
    WG: kf.kdb.LayerInfo = kf.kdb.LayerInfo(1, 0)
    WGCLAD: kf.kdb.LayerInfo = kf.kdb.LayerInfo(2, 0)


pdk = kf.KCLayout("FACTORIES_BEZIER_DEMO", infos=LAYER)
L = LAYER()

Basic call

bend_s = bend_s_bezier_factory(pdk)

b = bend_s(width=0.5, height=5.0, length=20.0, layer=L.WG)
print("S-bend:", b.name)
b

S-bend: bend_s_bezier_W0p5_H5_L20_LWG_NP99_TS0_TS1_ENone
png

Negative height

A negative height flips the offset direction.

b_flip = bend_s(width=0.5, height=-5.0, length=20.0, layer=L.WG)
b_flip
png

Curve resolution

nb_points controls the polygon resolution of the bezier backbone (default 99). Lower values trade smoothness for fewer vertices.

b_lo = bend_s(width=0.5, height=5.0, length=20.0, layer=L.WG, nb_points=20)
b_hi = bend_s(width=0.5, height=5.0, length=20.0, layer=L.WG, nb_points=200)
print("low-res vertices:", b_lo.shapes(L.WG).each().__next__().polygon.num_points())
print("hi-res  vertices:", b_hi.shapes(L.WG).each().__next__().polygon.num_points())

low-res vertices: 40
hi-res  vertices: 362

Cladding via LayerEnclosure

enc = kf.LayerEnclosure(
    sections=[(L.WGCLAD, pdk.to_dbu(2.0))],
    main_layer=L.WG,
    kcl=pdk,
)

b_clad = bend_s(width=0.5, height=5.0, length=20.0, layer=L.WG, enclosure=enc)
b_clad
png

Adding metadata

The factory accepts additional_info (a dict or callable returning a dict) that gets merged into KCell.info.

bend_s_meta = bend_s_bezier_factory(
    pdk,
    additional_info={"pdk": "FACTORIES_BEZIER_DEMO", "component_type": "bezier_sbend"},
)

b_meta = bend_s_meta(width=0.5, height=5.0, length=20.0, layer=L.WG)
print("cell info:", dict(b_meta.info))

2026-05-12 10:04:33.400 | ERROR    | kfactory.kcell:name:698 - Name conflict in kfactory.kcell::name at line 698
Renaming Unnamed_8 (cell_index=8) to bend_s_bezier_W0p5_H5_L20_LWG_NP99_TS0_TS1_ENone would cause it to be named the same as:
 - bend_s_bezier_W0p5_H5_L20_LWG_NP99_TS0_TS1_ENone (cell_index=0), function_name=bend_s_bezier, basename=None


cell info: {'pdk': 'FACTORIES_BEZIER_DEMO', 'component_type': 'bezier_sbend'}

See Also

Topic Where
Factory overview Factories: Overview
Euler S-bend (clothoid alternative) Factories: Euler
All-angle routing with S-bends Routing: All-Angle